Blend state in XNA

0
votes


I'm having difficulty figuring how to do something in XNA. I have something like this:

public void Draw()
{
     spriteBatch.Begin(SpriteSortMode.FrontToBack, BlendState.AlphaBlend);
     DrawFirstObject();    // Depth = 0.5f
     spriteBatch.End();

     spriteBatch.Begin(SpriteSortMode.FrontToBack, BlendState.Additive);
     DrawSecondObject();    // Depth = 0.2f
     spriteBatch.End();
}

Basically I need to have 2 different spritebatch begin calls one with AlphaBlend and one with Additive BlendState. But the problem is when I make this the drawn objects from the second call are always drawn on top of the first ones instead behind them where they need to be. I can't reformat my code so the second call is on the top and I need the keep the depth order. So I would be thankful if you have any suggestion.

1
c#xna
Why can't you re-order your code? If you want to alpha-blend, objects behind transparent objects have to be drawn first. There is no (easy) way around that. – Nico Schertler
I can't reorder my code because for example I have a tilemap object which draws the tiles which need to be with alpha blend and also I draw the tiles at different depths and the i call the Draw with Additive and draw some particles. This particles must be above some tiles and behind other but they are drawn above everything. – Rokner
Then you basically need to depth-sort your tiles and particles and issue spriteBatch.Begin() dynamically if you encounter a state change. It's probably possible to optimize this sorting procedure for minimal state changes but that would depend on your scene. – Nico Schertler

1 Answers

0
votes

As you are using transparent images in your first Draw call, ideally you should be using SpriteSortMode.BackToFront.

SpriteSortMode